Valve assembly



March 14, 1950 Filed March 26, 1945 L. A. MAJNERI VALVE ASSEMBLY 4Sheets-Sheet 1 1 INVENTOR.

LUDWIG A, MAJNERI ATTORNEYS March 14. 1950 MAJNERI 2,500,555

VALVE ASSEMBLY Filed March 26, 1945 4 Sheets-Sheet 2 FIG.2.

FIG-3 7s 46 e9 36 as 5 m a 73 & 8|

73 as 2 as INVENTOR. 32 LUDWIG AMAJNERI ATTORNEYS March 14, 1950 FiledMarch 26, 1945 FIGS.

L. A. MAJNERI 2,500,555

' INVENTOR.

LUDWIG A.MAJNERI ATTOVRNEYS L. A. MAJNERI VALVE ASSEMBLY Filed March 26,1945 FIG.6.

4 Sheets-Sheet 4 INVENTOR. LU DWlG A.MAJNERI ATTORNEYS Patented 14, 1950UNITEDSTATES PATENT, OFFICE I to The Warner Aircraf t Corporation,Detroit,

Mich., a corporation of Michigan This invention relates generally tovalve assemblies and refers more particularly to improvements in powervalves for. hydraulic brake systems. I

In certain hydraulic brake systems, it iseusw tomary to provide a powercircuit and a control circuit. ,The power 'circuitusually comprises abrake having a hydraulic actuator and an accumulator containing fluidundenrelatively high pressure. The control circuit ordinarily embodies amanually operable pressure producing device in the form of a mastercylinder and a reservoir for storing hydraulic fluid medium. The twocircuits'are frequently connected by a power valve which is initiallyoperated by the manually operable device to connect the accumulator tothe brake actuator for applying the brake. Inasmuch as the pressure inthe accumulator is relatively high, the brake actuator is practicallyinstantly operated to apply the brake regardless of the length oftheline between the actuator and accumulator. In many installations, theaccumulator pressure exceeds the desired brake applying pressure by. .asubstantial amount and in order to maintain the pressure at the brakeactuator within specified limits, the-power valve control plunger ineffect floats between a reservoir port and the port connected to theaccumulator. In

general, the arrangement is such that when the Application March is,1945, Serial No. 584,808

. 14 Claims. (01. 131-153) in one position of the valve membenregisterswith longitudinally spaced radial ports. respectively communicating withthe accumulator and brake actuator. Thus, fluid under pressure'from -theaccumulator enters the valve at right angles 'to the valve member andleaves the valve in a direction at right angles to the valve member.

Another object of this invention which contributes materially tostabilizing the action of the power valve is to provide -a constructionwherein the force opposing the control unit pressure anditending to movethe valve member in a direction to connect the brake actuator to thereservoir comprises fluid under substantially static pressure. Inaccordance with one embodiment, of this invention, the brake actuatorcommunicates with the space in the power valve at the end of the valvemember opposite the end exposed to the control unit pressure through arestricted port extending at right angles to the brake actuator port, soas to reduce the dynamic component of the fluid pressure admitted to thevalve to a minimum.

The restricted orifice previously mentioned also serves to dampenmovement of the valve member in the power valve and thereby assists inpreventing vibration or fluttering of the valve member. However, thisorifice will also function to introduce a time delay in the operation ofinstallations because of the tendency for the control plunger to flutterduring operation and in some cases, the plunger flutters so violentlythat it efiects proper control of'the brake applying pressure. Thisvibration or fluttering of the valve member or'control plunger islargely diie to the dynamic component of the control pressure acting onone end of the valve member and is overcome to a great extent by soarranging the valve ports that fluid under-pressure from the-accumulatorflows through the power valve to the brake actuator in directions atright angles to the direction of travel of the valve member. In detail,the valve member is provided with an annular groove in the outer surfacethereof which,

the valve member to connect the accumulator to the brake actuator and insome installations. this delay may be somewhat longer than is desired.It is, therefore, a further object of this invention to provide ,aconstruction having means for controlling the'orifice so that thelatter'does not materially restrict the'rate of movement 01" the valvemember to its brake applying position under the influence of the controlunit pressure. Still another object of this invention is to provideajpower valve havingcooperating means on the valve member and easingacting as a dash pot to dampen vibration of the valve member duringoperation of the power valve.

A further feature of this invention is to pro- Q vide a power valveconstructed in a manner to prevent leakage of fluid under pressure fromthe control circuit to the power circuit. This feature is especiallyadvantageous in installations where the brake is held in its appliedposition for long periods since it. prevents excessive loss of fluidfrom the control circuit during these periods.

The foregoing as well as other objects will he made more apparent asthis description proceeds, especially when considered in connection withthe accompanying drawings, wherein:

a valve assembly showing still a further modiflcation of this invention;and

Figure 6 is a, sectional view through still. another embodiment of thisinvention.

In Figure l of the drawings, I have illustrated a part of a hydraulicbraking system comprising generally a control circuit In and a powercircuit The control circuit l embodies a manually operated pressureproducing device l2 diagram matically indicated in Figure 1 as a mastercylinder having a piston l3 connected to a manually operated control I4through linkage 15.

* I The power circuit comprises an accumulator IS, a reservoir l'l,connected to the accumulator through the medium of a pump l8, and aground engaging wheel brake IS. The brake l9 may be any one of a numberof orthodox designs having brake friction means and a hydraulic actuator2| for the brake friction means.

y The accumulator I6 is adapted to contain a substantial supply ofhydraulic fluid under relatively high pressure and is connected to thebrake l9 by a valve assembly 22. The valve assembly. 22 comprises acasing 23 having a bore 24 therethrough and having a sleeve 25 securedwithin the bore 24. The ,sleeve .25 forms a wear resisting liner for thebore and the internal diam- 4 eter of the sleeve is predetermined toprovide a cylindrical valve chamber 26. One end 21 of the bore 24 isopen to enable the liner 25 to be sleeved into the bore and a cap 281issecured to the adjacent wall of the casing 23 130 close the end 21 ofthe bore. A suitable O-ring seal 29 surrounds the end 21 of the bore 24between the cap 28 and adjacent wall of the casing 23 to prevent theescape of fluid from the bore. The opposite endof the bore 24 is closedby the adjacent end wall 30 of the casing 23 and the latter wall of thecasing is formed with a port 3|. The port 3| establishes communicationbetween the valve chamber 26 and the lower end of the master cylinder I2for reasons to be presently set forth.

The casing 23 is provided with a second port 32, h which is connected tothe accumulator l 6, h

means of a conduit 33 and communicates with an annular groove 34formedin the periphery of the sleeve 25. The annular groove 34communicates with a second annular groove 35 formed in 3 theinnersurface of the sleeve 25 through the medium of radially extending portsor pas- I sages 36.

The casing '23 is formed with a third port 31 which communicates withthe reservoir The groove 39communicates with the interior of h thechamber 26 through the medium ofradi-al passages 40.

{ brake actuator 2| by a conduit42. The port 4| n 0o through the mediumof a conduit 38 and also communicates with an annular groove 38 formedin the periphery of the sleeve'25 in longitudinal spaced'relationship tothe annular groove 34.

4 communicates with an annular groove 43 formed in the periphery of thesleeve 25 intermediate th grooves 34 and 39. The annular groove 43communicates with an annular groove 44 formed in the inner surface ofthe sleeve 25 through the medium of radial passages 45.

Leakage of hydraulic fluid in an axial direction through the jointbetween the sleeve 25 and the bore 24 from one passageto another isprevented by suitable O-ring' seals. As shown in Figure 1, an O-ringseal 46 is located around the sleeve 25 to prevent the escape of fluidfrom the annular groove 34 through the end 2lof the bar 24. A secondO-ring seal 41 surrounds the sleeve 25 between the grooves 34 and 43 toprevent the escape of fluid from one groove to the other. A 7

third O-ring seal 48 surrounds the sleeve 25 between'the grooves 43 and39 to prevent the escape of fluid from one groove to the other. A fourthO-ring seal 49 surrounds the sleeve 25 between the groove 39 and theadjacent end of the sleeve to prevent the escape of fluid from thegroove 39 to the end of the chamber 26 adjacent the port 3 Supported inthe chamber 26 for sliding movement in opposite directions is a valvemember 5 i having a head 5| at the end thereof adjacent the port 3| andhaving an annular groove 52 intermediate the ends thereof. The end ofthe chamber 26 adjacent the port 3| is enlarged to Slidably support thehead 5| on the valve member. Th engaging surfaces of the head and sleeveare pref erably lapped to provide a fluid seal therebetween. However,instead of providing lapped surfaces, an O-ring seal may be employed toprevent the escape of fluid underpressure through the joint betweenthehead 5| and the adjacent surface of the chamber '26. f

The reduced end 52' of the valve member is provided with a recess 53 anda spring 54 is positioned in the recess; One end of the spring 7 abutsthe end wall 55 of the recess 53 and the opposite end of the springabuts the cap 28. The

arrangement is such that the valve member is normally urged by thespring 54 in a direction 45 toward the end wall 30 of the casing 23.

The valve member 50 is moved against the action of the spring 54 bymanual operation of the control member l4. which moves the piston .|3downwardly in the master cylinder to supply 50 fluid under pressure intothe chamber 26 through the port 3|. The length of the groove. 52 ispredetermined to connect the groove 44 with the reservoir port 3| whenthe valve member 50 is in its inoperative position shown'in Figure landto connectthe groove 44 with the groove 35 when the valve member ismoved by the master cylinder in a direction toward thecap28. Thus, whenthe valve member is in its inoperative position, the brake actuator 2|isconnected to the reservoir through-the port 31 and when the valvemember is in its. operative position. the brake actuator 2| is connectedto the accumulator l6. As a. result, fluid under relatively highpressure from the accumulator I6 is admitted to the brake actuator-2l toapply the brakefrictionmeans 20. In connection with theabove, attentionis again calledto the fact that the passages 36 and 45 extend radiallywith respect to the direction of movement of the valve member 50 in thechamber 26. Thus, when the valve member 50 is in a position whereinthegroove 52 connects the passages 36 and 45, fluid 'under pressure flowsthrough the passage 36 into the groove at right angles to the directionof movement of the valve member.

.Owing to the fact that the pressure in the accumulator I6 is usuallyconsiderably higher than the actual pressure required to operate thebrake, it is desirable to control this pressure to maintain the latterbelow a predetermined critical value. For accomplishing this result,provi-' sion is made herein for communicating the substantially staticpressure in the brake port 4! to the chamber 26 opposite the reduced end62" of the valve member. As shown in Figure 1 of the drawings, arestricted passage 66 extends at right angles from the port 4| to apassage 61 formed, in the cap 26 and communicating'with the adjacent endof the chamber 26. Thus, fluid under pressure is permitted to flow fromthe brake port 44 at a reduced rate to thechamber 26 at the end 62' ofthe valve member 66 and this fluid is compelled to leave the port 4| atsubstantially right angles to the flow of fluid through this port. As aresult, the pressure in the chamber 26 at the end 62' of the valvemember may be considered as the static pressure of the fluid in theport4|, because it is not eflected by the flow of the fluid through the port4|.

As the so-called static pressure in the chamber 26 at the end 62 of thevalvemember increases beyond the desired brake-applying pres:- sure, thevalve member is moved toward the wall 30 of the casing and closes thepassages 26, which are connected to the accumulator l6. In the event thestatic pressure continues to rise, the valve member 66 moves in theabove direction sufllciently to connect the passages 46 with thepassages 40 through the groove 62 to permitfluld under pressure fromthe-brake port 4| to escape into the reservoir l1. As soon as thepressure l acting on the reduced end 62 of the valve drops below thepredetermined critical-value, the valve member 62 is again moved againstthe action of the spring 64 to close communication between the reservoirport 21 and the brake port 4|. Thus the valve member 66, in efiect,floats in.

a the chamber to accurately control the pressure at the brake actuator2|. H

It has been pointed out above that the pas-, sage 66 lsrestricted. Thepurpose of this restriction is to delay the pressure rise in the chamber26 at the reduced end 62' of the valve member and thereby avoidpremature movement of the valve member to connect the brake port 4| withthe reservoir port 31. However, the restricted passage 66 also retardsthe flow oi fluid from the chamber26 to the brake port when the valvemember is moved against the action of the spring 64 by the mastercylinder l2. It follows, therefore, that the diameter of the passage 66must be proportioned to givethe .optimum valve action in eitherdirectionof movement of the valvemember 66.

Attention is alsocalled to the fact that the ratio between the diameteroi. the head 6| on the valve member 66 and the area of the reduced end62' of the valve member is predetermined to afiord the desired pressurediii'erential between the control unit pressureand the brake applyingpressure. In the present embodiment of the invention, the pressure ofthe fluid from the master cylinder l2 acts on a substantially greaterarea of the valve member than the brake applying pressure in thechamber" at the reduced end or the valve member. Accordingly. thepressure required to manually operate the valve member to apply thebrake is correspondingly less than the actual brake applying pressure.

Figure 2 of the drawings illustrates a valve assembly having provisionfor retarding the pressure rise in the chamber 26 at the reduced end 62'of the valve member 66. In detail, the cap closing the end 21 of thebore 24 is fashioned to form a chamber 66 having a vented wall 6i at oneend and having the opposite end communicating with the passage 61. Aplunger 62 is slidably supported in the chamber 66 and is provided witha reduced end 63 normally urged into abutting engagement with theadjacent end of the sleeve 26 by means of aspring 64. The spring 64 isarranged under compression between the plunger 62 and the wall 6| thechamber 66. An O-ring 66 surrounds the plunger 62 intermediate the endsof the latter and engages the inner surface 01' the chamber 66 toprevent the escape of fluid under pressure around the plunger.

The displacement obtained by the available travel of the plunger 62 inthe bore 66 is substantially greater than the displacement of fluid dueto the travel of the valve member 60 from v the released position shownin Figure 2 of the drawings to its brake applying position where thegroove 62 connects the ports 32 and 4|. Thus, it will be readily seenthat for this part of the travel of the valve member 66, movement of theplunger is not dependent on the flow of fluid through the restrictedoriflce 66 into the port 41, but is restricted only by the very light Ispring 64 acting on th plunger 62. As'soon as a pressure rise isobtained in the port 4|, fluid under pressure will flow from the port 41through the restricted passage 66 to' the passage 61 and The plunger 62will also materially :assistf'in' releasing the brakes. For example, ifat the instant when the pressure in the port 2| is released. the plunger66 is in a position where the groove 62 is registering, or almostregistering, with the groove 36, then the valve member 66 has to move asubstantial distance before it can establish communication between theports so 4| and 61. With the plunger 62 provided, this movement of thevalve member is not dependent on the additional fluid passing throughthe restricted passage 66, because fluid is readily supplied into thepassage 6! by movement of the g5 plunger 62 by the spring 64.

With the above exceptions, the construction is the same as the one shownin Figure l of the drawings and corresponding parts are indicated by thesame reference characters.

7o The'embodiment of the invention illustrated in Figure 3 of thedrawings shows a valve assembly equipped with a somewhat different typeof valve member. This valve member is indicated generally by thereference character 66 76 and the end portion of the latter adjacent toport 1 3| is axially bored to form a cylindrical chain- 1 the oppositeend of the valve member. The enber 61 having a reduced portion 66adjacent 1 of the valve member through the medium of i radial ports H.

The groove '16 corresponds to the groove 52 in the valve member 50 ofthe first described form of this invention in that it alternativelyconnects the brake actuator port ll to the accumulator and reservoirports 32 and 31 respectively upon movement of the valve 1 member 66 inopposite directions in the valve chamber 26.

The reduced portion 66 of the chamber 61 communicates with the chamber26 at theend I2 01' the valve member through a port 13. Thus, p

it will be noted that the reduced portion 68 of the-chamber 61 forms apassage between the I ports H and I3 to enable fluid underpressure toflow from the brake port 4! to the chamber 1 Nat the end 12 of the valvemember.

In the present instance, a differential flow or fluid in oppositedirections through th passage 68 is obtained by providing a-plunger I3in the passage 68. The plunger I3 is provided with a spring I6 heldunder compression between the head 14 of the plunger and a plug 'I'Isecured in the enlarged portion 69 of the valve chamber The aboveconstruction is such that when the i valve member 66 is in its brakeapplying position wherein the groove I connects the ports ti and 32, itwill be noted that the plunger I3 is in its closed position with respectto the passage 68. However, fluid underpressure from the 1 brake port Mis permitted to flow through the ports II and through the restrictedport 15 in 1 the plunger to the chamber 26 at the end I2 oi the valvemember.

The restricted port I is so arranged that the pressure communicated 1therethrough corresponds substantially to the static pressure at thebrake port 4| to obtain the same results previously discussed inconnection with the first described form of this invention.

may be restricted to obtain the desired delay in In the presentinstance, however, the port I5 movement of the valve member toward itsclosed or inoperative position without regard to unduly I retardingmovement of the valve member to its open position. In this connection,it will be noted 3 that asthe valve member is moved from the 1positionshown in Figure 3 to itsopen position I against the action ofthe spring 54, fluid under pressure flows relatively freely through theport 1 l3 and moves the plunger I3 to its open posi- 1 tion. As shown,the plunger is axially bored and is provided with radial ports I8intermediateits 3 ends to facilitate the escape of. fluid from thepassage to the enlarged portion 69 of the chamj ber 61.

plunger I3 is applicable in valve assemblies where r i It follows fromthe above that the it is desired to eliminate the time delay in applyingthe brake, which may result in the use of a fixed restricted passagebetween'the brake port and the valve chamber.

- 24 is provided with an axially extending cham- The valve assemblyshown in Figure 3 also diflers from the previously describedconstructions in that provision is made for retarding or dampingmovement of the valve member to its brake applying position. In detail,it will be noted that the cap 19 for the end 21 of the bore ber 60 forreceiving a cylindrical projection 8| on the adjacent end of the'valvemember 66. The iconstruction'is such that the projection 6| enters thechamber 60 just prior to opening communication between the brake port 4|and the accumulator port 32. This feature tends to stabilize the actionof the valve member and to preventflutterlng oi the latter.

A further feature of the valve assembly shown in Figure 3 is that thevalve'member 66 is operated from the master cylinder I2 through-a piston82 slidably supported in an extension 69 of the chamber 26 and normallyurged-against the port 3| by a spring 64. The spring 84 is actuallystronger than the spring 54, but in the surrounds the piston to preventthe escape or fluid from-the port 3| past the piston. This constructionis advantageous where it is desired to provide greater pedal travelduring brake application than can be'ordinarily obtained where the valvemember is operated directly by the fluid under pressure from the mastercylinder. Moreover, by providing a flxed'stop 81 for the piston 82, itis possible to limit the amountof pressure I applied to the valve member66 and this is especially advantageous in installations (not shown)wherein the accumulator may be selectively connected to the port SI forparking purposes. 1

With the above exceptions, the bly shown in Figure 3 operatesin'substantially the same manner as the valve assembly shown port 96.The restricted port '96 connects the an-' nular groove '62 intheperiphery'of the valve memberto the axially extending bore 53 in thevalvemember. This bore is open at the reduced end 52' of the valvemember and, in the present instance, is provided with an extension 6|,which communicates with the 'chamber26 through a port 92. The port 92 ispositioned at the inner side of the head 5| on the valvemember 50 sothat the fluid pressure admitted through the port acts upon an area ofthe valve member which is equal to. the. area of the valve memberexposed to the master cylinder l2. Thus, the same pressure is providedat opposite ends of the valve member during brake application andleakage past the head 6! of the valve .member in instances ofprolongedbr'ake application 'is prevented. I

In the valve assembly shown in Figure 4 of the valve assem drawings,movement of the valve member 66 to its brake applying position isretarded by a dashpot arrangement indicated generally by the ref- Withthe above exceptions, the valve assembly shown in Figure 4 is the sameas the one shown in Figure 1 and corresponding parts are, therefore,indicated by the same reference numerals.

The modification shown in Figure 5 of the drawings diflers' from x theone previously described in thatcommunication between the restrictedport 66 and the end of the chamber 26 opposite the reduced end 62 of thevalve member 56 is prevented by a plug I66 secured in the bore 63 of thevalve member 66 and havingan O-ring manner that the pressure of thisfluid is not effected by turbulence of the fluid under pressure flowinginto the port 42 from the passage 46. In other words, fluid underpressure entering the restricted port I68 is compelled to flow throughthe restricted annular passage I61 from the port 42 and any turbulenceexisting would have a negligible efl'ect on the' pressure of the fluidin the chamber I66.

It will also be noted from Figure 6 of the draw- "ings that thevalvemember 66 is axially bored to form'achamber I69 having the endadjacent the seal IM to prevent the escape of fluid around the 3 same.Thus, fluid under pressure from the restricted port 66 is compelled toflow through the port 92 into the valve-chamber 26 and acts on the innerface of the head 6| tending to move the valve member to the positionthereof shown in Figure 5; Also the reservoir I1. is connected to thechamber 26 at the reduced end 62' of the valve member 56 by a passageI62. Thus, during brake application, the pressure in the chamber 26 atthe inner face of the head SI of the valve member 52' is greater thanthe pressure applied to the outer face of the head II of the valvemember by the master cylinder I2. This is particularly desirable incases where the valve member is held in its brake applying position forsubstantial periods of time, because any leakage pastthe head 5| willtake place from the power circuit to the control circuit where theexcess fluid may be readily drained oil. With the above exceptions, theembodiment of the invention shown in Figure 50f the drawings is the sameas the construction illustrated in Figure 4 and," accordingly,corresponding parts are indicated by the same reference characters.

Figure 6 of the drawings illustrates a valve assembly similar in manyrespects to the embodiments of the invention shown in Figures 1 and 2 ofthe drawings. However, Figure 6 of the drawings features asomewhatdifl'erent arrangement for communicating the substantiallystatic pressure of the hydraulic brake fluid'in the brake actuatorpassage M to the chamber 26 at the reduced end 52' of the valve member56. Also, Figure 6 of the drawings illustrates a slightly different formof displacement device than is shown in Figure 2 of the drawings.

In detail, the port 42 through the valve casin 23 is provided with abushing I65 having the inner end reduced to form an annular chamber I66, which communicates with the radial passage 45 through the medium ofa restricted annular passage I61. The annular chamber I66 is connectedto the passage 51 by means of a restricted port I68 and the" passage 51communicateswith the valve chamber 26 at the reduced end 52' of thevalve member 56. In some installations, the above construction may bepreferred, because it insures transmitting fluid from the brake cap '26open and having the opposite end closed by the head 5| on thevalve-member, except for a small vent II6, which communicates with thereservoir port 31. v A plunger III is slidably mounted in the chamberI66 and is n'ormally urged into engagementf'with the split ring II2 by acompression spring H3. The ring 2 is suitably securedin the chamber I66adjacent the open end of the latter and also forms an abutment for thereturn spring 64. I

Assuming that the valve member 56is'in the position thereof shown inFigure 6 of the drawings, and that fluid under pressure is admittedthrough the port 3|, it will be noted that the valve member 56 ismovedin the chamber 26 toward its'brake applying. position. As the valvemember 56 moves in the above direction, the pressure of the fluid in thechamber. 26 at the reduced end 52 of the valve member actson the plungerII I and moves the plunger against the "action of the-spring II3.However, the construction is such that the plunger does not move to thelimit of its travel by the spring II3 until the passage 45 is connectedto the accumulator passage 36 through the annular groove 52. When thiscondition exists, fluid under pressure is transferred from this brakeactuator port 42 through the restricted passage I66 to the chamber 26 atthe reduced end 52' of the valve member. This pressure rise in thechamber 26 effects a continuation of the movement of the plunger IIIagainst the action of the spring I I 3 to increase the volume of theportion of the chamber I 69 connected to the valve chamber 26. Thus, thechamber I69 and plunger III form a displacement device, which delaysmovement of the valvemember 56 in a direction toward its brake releasingposition.

While a number of constructions are shown herein for the purpose ofillustrating the present invention, nevertheless, each embodimentfeatures a valve assembly wherein fluid under pressure flows to and fromthe valve in such a manner that no force components are created tendingto move the valve member in either of its two directions, of movement.It will further be noted that in each modification, provision is madefor Y flutter during operation.

. nally from the flrstport, a third port spaced from both the aboveports, a valve member slidable in the chamber and having an annulargroove in the periphery thereof alternatively connecting the second portto the first and third between the first and second ports, the diameterof the restricted passage bein so proportioned with respect to thediameter of the second port to insure a substantial delay in thepressurerise in said chamberat the side aforesaid of the valve-surface i2. A valve, assembly for hydraulic brake systems having a cylindricalchamber, a first port extending radially outwardly from thechamber, asecond port spaced longitudinally from the first port and extendingradially outwardly from the.

chamber, a third port spaced from both the above ports, a piston typevalve member slidable in the chamber and having an .annular groovein'the periphery thereof alternatively connecting the second port to thefirst and third ports upon movement of the valve member in oppositedirections, a fourth port in thevalve chamber for supplying fluid underpressure to the chamber at one end of the valve member to move thea,soo,sss

' the other surface on the valve member to move latter in a direction toconnect the second port to the first port through said annular groove,and means for communicating the substantially static pressure ofthefiuid in the second port to the chamber at the opposite end of the valvemember to urge the latter in a direction to connect the second and thirdports through said annular groove. 8. A valve assembly for hydraulicbrake systems having a cylindrical chamber, a first .port extendingradially outwardly from the chamber, a. second port spacedlongitudinally from the first port and extending radially outwardly fromthe chamber, a third port spaced from both the aboveports,a piston typevalve member slidable in the chamber and having an annular groove intheperiphery thereof alternatively connectingthe second port to thefirst and third ports upon movement of the valve member in oppositedirections, a fourth port in the valve chamb'er for supplying fluidunder pressure to the chamber at one end of thevalve member to move thelatter in a direction to connect the second port to the first portthrough said annular groove, and a restricted passage connecting thesecond port to the chamber at the opposite 'endof the valve member andarranged to transfer the substantially static pressure of the fluid inthe second passage to the chamber at the last-named end of said valvemember.

4. A valve assembly for hydraulic brake systems" having a cylindricalchamber, a port; in said chamber, a second port in said chamber, a thirdport in the chamber, a valve member slidably supported "in the chamberfor alternatively connecting the third port to the first and secondports upon movement of the valve member in opposite directions, saidvalve member having axially spaced surfaces against which fluid underpressure is adapted to act, a fourth-port comthe latter in a directionto close communication between the first and third ports.- Y 5. A valveassembly for hydraulic brake systems comprising a casing having acylindrical chamber provided with an enlargement at one end, a pair oflongitudinally spaced ports in the casing, a port'intermediate the portsaforesaid, a valve member supported in'the chamber for sliding movementandhaving an annular elongated groove in the periphery alternativelyconnecting the intermediate port to the endports upon movement of thevalve member inopposite directions in thechamber, axially spacedportions on the valve member against which fluid under pressure isadapted to act to impart movement to the valve member, one of saidportions presenting a larger area to fluid under pressure than the otherand being located in the enlargement of the chamber, an axial passage inthe .valve member communicating with the chamber at the inner side ofsaid one portion and communicating with the chamber beyond the other..portion on the valve member, and a restricted passage extendingsubstantially radiallyfrom the axial passage to said annular groove inthe periphery of the valve member.

6. A valve assembly for hydraulic brake systems, comprising a chamber, avalve member of the piston type slidably supported in the chamber andhaving axially spaced surfaces presenting different areas against whichfluid under pressure is adapted to act, a port in the chamber positionedto supply fluid under pressure to the chamber against the valve surfaceof reduced area, a second port in the chamber spaced from the firstport, a third port in the chamber, a fourth port in said chamberpositioned to introduce fluid under pressure into the chamber againstthe surface of enlarged area on the valve member, means associatedwiththe valve member for alternatively connecting the third port to thefirst and second ports upon movement of the valve member in. oppositedirections, and a restricted passage arranged to communicate thesubstantially static pressure of the fluid in the third port to thechamber adjacent the surface of reduced area on the valve member to movethe latter in a direction to close communication between the first andthird ports.

'7. A valve assembly forhydraulic brake systems, comprising a chamber, apiston type valve member supported in the chamber for sliding movementand having axially spaced surfaces against which fluid pressure may act,a port in said chamber positioned to supply fluid to said chamberadjacent one of the surfaces on the municating with the-chamber at oneside-of one of said surfaces on the valve member for advalve member,second and third ports in said chamber, a fourth port in said chamberlocated to supply fluid under pressure to the chamber adjacent the othersurface on said valve member, means associated with the valve member foralternatively connecting the third port to the first and second ports inresponseto movement of the valve member in opposit directions in thechamber, and means operating in timed relation to movement of the valvemember in a direction to connect the first and third ports to dampencontinued movement of the valve member in said latter direction.

8. A valve assembly for hydraulic brake systems, comprising a chamber,first and second ports in the chamber, a third port spaced from g boththe above ports, a fourth'port in the chamin the third port tothechamber at the side or '75 ber, a valve member slidable in the chamberand vhaving means for, thcsecondporttothefirstandthirdportsin responseto movement of the valve member in opposite directions, a surface on thevalve member adapted to be acted upon by the fluid under pressureadmitted to the chamber through the first port for moving the valvemember in a direction to connect the second port to the third port,another surface on the valve member adapted to be acted upon by thefluid admitted to the chamber through the fourth port to-move the valvemember in the opposite direction to connect the first port to the secondport, means for communicating the substantially static pressure of thefluid in the second port to the chamber adjacent the first mentionedsurface on the valve member tending to move the valve member in adirection to connect the second and third ports, and means responsive tomovement of the valve member in the opposite direction'to retard,continued movement of the said valve member in the latter direction.

9. A valve assembly for hydraulic brake; systems, comprising a casinghaving a. chamber,

ranged with respect to one another-and with respect to the first andsecond ports, a valve member slidably supported in the chamber andhaving means for alternatively connecting the third port face on thevalve member adapted to be acted the chamber, a. valve member supportedin the chamber for sliding movement and having an annular elongatedgroove in the periphery thereof responsive to movement of the valvemember in opposite directions to alternatively connect the third port tothe first and second ports, axially spaced surfaces on the valve memberadapted to be respectively acted -upon by fluid under pressure admittedto the chamber through the first and fourth ports, a third surface onthe valve member against which pressure is adapted to be applied andlocated intermediate the above surfaces, and a fluid passage in thevalve member communicating-with the chamber adjacent the intermediatesurface and having a restricted communication with the annular groove insaid valve member.

10. A valve assembly for hydraulic brake sys-. tems comprising a casinghaving a cylindrical chamber provided with an enlargement atone end, apair of first and second longitudinally spaced ports in the casing, athird port intcrmediate the ports aforesaid, a valve member supported inthe chamber for sliding movement and having an annular elongated groovein the periphery alternatively connecting the intermediate port to theend ports upon movement of the valve member in opposite directions inthe chamber, a surface on the valve member adapted to be acted upon byfluid under pressure admitted to the chamber through the first port tomove the valve member in a direction to connect the second port to thethird port, an enlargement on the valve member slidable in the enlargedend of the chamber, a fourth port in the chamber positioned to supplyfluid under pressure to the chamber at the outer side of the enlargementto move the valve member in a direction to connect the first and secondports, an axial passage in the valve member-communicating with thechamber at the inner side of the enlargement, and a restricted passageextending outwardly from the axial passage to said annular groove in theperiphery of the valve member.

11. A valve assembly for hydraulic brake systems, comprising a casinghaving a chamber, first and second ports in said chamber, third andfourth ports in said chamber predeterminedly arupon by fluid pressureadmitted to the chamber v through the fourth port for moving the valvemember in a direction'to close the second port and to connect the firstand third ports, means for communicating the substantially staticpressure of the fluid in the third port to the chamber adjacent thefirst surfacaand a displacement device responsive to the fluidunder'press'ure ad-' *mitted to chamber by the last named meansto thechamber and having means for alternatively connecting the third port tothe first and second ports upon movement of the valve member in oppositedirections, a surface on the valve member adapted to be acted upon byfluid pressure admitted to the chamber through the first port formovingsaid valve member in a direction to close the first port and to connectthe second and third ports, a second surface on the valve member adaptedto be acted upon by fluid pressure admitted to the chamber through thefourth port for moving the valve member in a direction to close thesecond port and to connect the first and third ports, means focommunicating the substantially static pressure of the fiuid in thethird port to the. chamber adjacent the first surface, and means carriedby the valve member and operated by fluid pressure admitted to thechamber by the last named means to delay movement of the valve member ina direction to close communication between the first and third ports.

13; A valve assembly fo hydraulic brake systems, comprising a casingprovided with a chamber having first, second, third and fourth portspredeterminedly arranged with respect to one another, a valve memberslidably supported in the chamber and having means for alternativelyconnecting the third port to the first and second ports upon movement ofthe valve member in opposite directions, a surface on the valve memberadapted to be acted upon by fluid pressure admitted to the chamberthrough the first port for moving said valve member in a direction toclose the first port and to connectthe .second and third ports, a.

on the valve member acted upon by fluid under pressure admitted to thechamber through the first port.

.ber ha .14. 1 valve assembly for hydraulic brake systems, comprising acasing provided with a chamving first, second, third and fourth portspredeterminedly arranged .with respect to one another, a valve memberslidably supported in the chamber and having means foralternativelyconnecting the third port to the first and second ports upon movement ofthe valve member in opposite directions, a surface orifthe valve memberadapted to be acted upon by fluid pressure admittedto the chamberthrough the first port for movin: said valve member a direction to closethe first port and to conn t the second and third 16,.- nmmcns crrsnTh'e'following references are of record in the file of this patent: I

" STATESPATENTS Number Number Name Date Brown Apr. 14, 1896 Iverson Apr.6, 1926 Cash June 12,1934 Pardee July 30, 1935 Besler Oct. 13, 1936Vorech Nov. 17, 1936 Sanford Nov. 22, 1938 Beggs July 25, 1939 Kenyon-Aug. 13, 1940 Stelzer Oct: 28, 1941 Herman May 12, 1942 Towler June 9.1942 Rockwell 1 Dec. 22, 1942 Mathys Dec. 3, 1946 FOREIGN PATENTSCountry Date Germany June 15, 1934 France Dec. 15, 1934

